Anticancer agents based on regulation of protein prenylation

ABSTRACT

Oncoproteins such as Ras and RhoB are known to induce cell division in an unrestrained manner when such proteins are localized at the inner surface of a cancer cell membrane. The localization is effected by the prenylation reaction, whereby a hydrophobic group (e.g. a farnesyl group) is attached to the protein in the presence of an enzyme (e.g. farnesyl protein transferase). Deactivation of the prenylation enzyme through covalent modification can therefore ultimately result in the mitigation and/or cessation of cancer cell growth. Various prenylation inhibitors having the necessary structural groups to bond covalently, or essentially irreversibly, to the prenylation enzyme include carbonyl or thiocarbonyl compounds (or masked versions of these compounds) and alpha oxo-epoxides bonded to a hydrophobic, substrate-mimicking group. The carbonyl or thiocarbonyl compounds also contain a nucleofugal atom or group to enhance the tendency to form covalent bonds.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from Provisional ApplicationSerial No. 60/241,955 filed Oct. 23, 2000, the disclosure of which ishereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

[0002] The present invention relates to the prevention and/or treatmentof cancer by inhibiting enzyme-catalyzed prenylation reactions thatallow localization of Ras, RhoB, and other proteins at the innersurfaces of cancer cell membranes and other intracellular locations,thereby causing unrestrained cell division.

BACKGROUND OF THE INVENTION

[0003] Approximately 25% of all human cancers result from a mutant genethat encodes a mutant form of the protein known as Ras. In cancer cells,Ras activates the cells to divide in an unrestrained manner. To inducecell division, Ras must be localized at the inner surface of the cancercell membrane. This membrane localization of Ras is effected byattachment of a hydrophobic group, typically the farnesyl group, butpossibly the related geranylgeranyl group. In either case, the groupbecomes attached to Ras enzymatically in a process known as prenylation.Thus, interference with prenylation of Ras has the potential to preventRas localization at the inner surface of the cancer cell membrane,resulting in the cessation of unrestrained cell division and/orreversion of the cancer cell to a normal phenotype.

[0004] The enzyme that attaches the farnesyl group to Ras, RhoB, andother proteins to facilitate the proper localization of these proteinsin the cell is farnesyl protein transferase, also known as proteinfarnesyltransferase (referred to here as FTase). The farnesyl groupbecomes attached to Ras, RhoB, and other proteins by reaction withfarnesyl diphosphate, also known as farnesyl pyrophosphate (referred tohere as FPP). In other words, FTase catalyzes the reaction illustratedbelow for the Ras protein, in which the protein becomes attached to thefarnesyl group by displacement of pyrophosphate (P₂O₇ ⁴⁻, referred tohere as PP_(i)):

FTase .

Ras+FPP→farnesyl-Ras+PP_(i)

[0005] Thus, a key target in a strategy to retard cancer cellproliferation is the enzyme FTase. By regulating FTase activity, Rasfarnesylation, RhoB farnesylation and geranylgeranylation, and theprenylation of other proteins can be controlled. This can alter theintracellular distribution of these proteins and in turn prevent cancercells from proliferating. Because normal cells also require FTaseactivity, the optimal regulation of prenyltransferase activity must bedetermined empirically.

[0006] Many substances are known to block FTase activity and preventfarnesylation of cellular proteins. These include inhibitors of theenzyme FTase, which generally operate by blocking the binding ofproteins to be prenylated, FPP, or both, to the FTase active site.Without the ability of the normal substrates (e.g. Ras and FPP) to bindto FTase, this enzyme can no longer transfer the farnesyl group from FPPto Ras. In general, inhibitors structurally mimic one or both of thenatural substrates of the enzyme, in this case Ras and/or FPP. Forconventional inhibitors, their binding to FTase is reversible andnoncovalent (i.e. the binding of the inhibitor to FTase does not involvethe formation of covalent bonds). Instead, hydrophobic forces, hydrogenbonding, electrostatic attraction, etc. are principally responsible forbinding of the inhibitor to the enzyme FTase. These binding forces allowthe inhibitor to block the site on FTase where the normal substratesneed to bind for farnesylation of Ras to occur.

[0007] It would therefore be desirable to develop a method ofpreventing, substantially irreversibly, FTase from farnesylating Rasand, more generally, preventing other prenylation enzymes from promotingthe inner cell membrane localization of oncoproteins. Interaction ofFTase, for example, with substances that covalently modify the activesite of FTase should result in an enzyme with an essentially permanentreduction in catalytic ability. In principle, and in contrast toconventional enzyme deactivation, the covalent attachment can beirreversible or nearly irreversible. The desirable characteristics of aprenylation enzyme inhibitor may include both a substrate-mimickinggroup as well as a group having the ability to bond covalently to theenzyme at or near its active site.

SUMMARY OF THE INVENTION

[0008] The present invention is directed to methods for inhibiting aprenylation enzyme In one embodiment, the method comprises contacting aprenylation enzyme with a prenylation enzyme inhibitor of the followingstructural Formula I:

[0009] or a pharmaceutically acceptable salt, prodrug, or ester thereof,

[0010] where A₁, A₂, and A₃ are independently selected from the groupconsisting of hydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy,cycloalkoxy, alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl,alkanoyl, aroyl, aminocarbonyl, aminoalkanoyl or optionally substitutedaminoalkanoyl, carbocycloalkyl or optionally substitutedcarbocycloalkyl, heterocyclo or optionally substituted heterocyclo,heteroaryl or optionally substituted heteroaryl, aryl, aralkyl,(heterocyclo)alkyl, (heteroaryl)alkyl, alkoxycarbonyl, alkylcarbonyloxy,alkoxyalkanoyl, and carboxyalkyl, and A₄ is selected from the groupconsisting of hydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy,cycloalkoxy, alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl,alkanoyl, aroyl, aminocarbonyl, aminoalkanoyl or optionally substitutedaminoalkanoyl, carbocycloalkyl or optionally substitutedcarbocycloalkyl, heterocyclo or optionally substituted heterocyclo,heteroaryl or optionally substituted heteroaryl, aryl, aralkyl,(heterocyclo)alkyl, (heteroaryl)alkyl, alkoxycarbonyl, alkoxyalkanoyl,carboxyalkyl, amino or substituted amino, amido or substituted amido,and alkanoylamido, with the proviso that A₁, A₂, A₃, and A₄ are not allhydrogen. In a preferred embodiment, A₁, A₂, A₃, and A₄ areindependently selected from the group consisting of hydrogen, alkyl,alkenyl, alkynyl, aryl, aralkyl. In another preferred embodiment, atleast one of A₁, A₁, A₃, and A₄ is a branched alkenyl, which may bespecifically a farnesyl or geranylgeranyl group. In another preferredembodiment, the group A₄ is selected from the group consisting ofhydrogen, alkyl (e.g. methyl), haloalkyl (e.g. trichloromethyl,trifluoromethyl, perfluoroethyl), aryl (e.g. phenyl), and heteroaryl(e.g. 4-pyridyl).

[0011] In another preferred embodiment, the prenylation enzyme inhibitoraccording to the method has the following structural Formula II:

A—Y—(C═Z)—CX₁X₂X₃  (Formula II)

[0012] or a pharmaceutically acceptable salt, prodrug, or ester thereof,

[0013] where Y is a heteroatom or heteroatomic group selected from thegroup consisting of O, NH, NA′, and S; where,

[0014] when Y is O, A and A′ are independently selected from the groupconsisting of hydrogen, alkyl, alkoxyalkyl, alkylthio, alkenyl, alkynyl,cycloalkyl, haloalkyl, carbocycloalkyl or optionally substitutedcarbocycloalkyl, heterocyclo or optionally substituted heterocyclo,heteroaryl or optionally substituted heteroaryl, aryl, aralkyl,(heterocyclo)alkyl, (heteroaryl)alkyl, carboxyalkyl, amino orsubstituted amino, amido or substituted amido, and alkanoylamido;

[0015] when Y is S, A and A′ are independently selected from the groupconsisting of hydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy,cycloalkoxy, alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl,carbocycloalkyl or optionally substituted carbocycloalkyl, heterocycloor optionally substituted heterocyclo, heteroaryl or optionallysubstituted heteroaryl, aryl, aralkyl, (heterocyclo)alkyl,(heteroaryl)alkyl, carboxyalkyl, amino or substituted amino, amido orsubstituted amido, and alkanoylamido; and,

[0016] when Y is NH or NA′, A and A′ are independently selected from thegroup consisting of hydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy,cycloalkoxy, alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl,alkanoyl, aroyl, aminocarbonyl, aminoalkanoyl or optionally substitutedaminoalkanoyl, carbocycloalkyl or optionally substitutedcarbocycloalkyl, heterocyclo or optionally substituted heterocyclo,heteroaryl or optionally substituted heteroaryl, halo, aryl, aralkyl,(heterocyclo)alkyl, (heteroaryl)alkyl, alkoxycarbonyl, alkylcarbonyloxy,alkoxyalkanoyl, carboxyalkyl, amino or substituted amino, amido orsubstituted amido, and alkanoylamido;

[0017] Z is oxygen or sulfur; and,

[0018] X₁, X₂, and X₃ are independently selected from the groupconsisting of hydrogen, oxygen, halogen, organosulfonyloxy,bromobenzenesulfonyloxy, methanesulfonyloxy,trifluoromethanesulfonyloxy, acyloxy, aryloxy, imidazolyl, —O—N═O, —NO₂,—OSO₃ ⁻, and —OPO₂(OH)⁻, with the proviso that X₁, X₂, and X₃ are notall hydrogen. In a preferred embodiment, A, and optionally A′, areindependently selected from the group consisting of hydrogen, alkyl,alkenyl, alkynyl, aryl, aralkyl. In another preferred embodiment, atleast one of A, and optionally A′, is a branched alkenyl, which may bespecifically a farnesyl or geranylgeranyl group. Preferably, at leastone of X₁, X₂, and X₃ is a nucleofugal group capable of bonding with theactive site of a prenylation enzyme.

[0019] According to the possibilities for Formula II, there exists acarbonyl variation, where Z is oxygen, and also a thiocarbonylvariation, where Z is sulfur. In the case of the carbonyl variation, apreferred class of prenylation inhibitors is obtained when X₁ is oxygen,such that the inhibitor will now have two carbonyl functions, and X₂ ismethyl. These preferred compounds may also be categorized as pyruvicacid derivatives.

[0020] In another embodiment, a method of screening compounds aspotential anti-tumor agents comprises contacting a prenylation enzymewith a test compound according to Formula I or Formula II. The methodfurther comprises measuring prenylation activity of the enzyme toidentify candidate anti-tumor agents. In a more specific embodiment,prior to the contacting step, a natural substrate of the prenylationenzyme (e.g. farnesyl pyrophosphate and/or geranylgeranyl pyrophosphate)is added to the test compound to compete therewith and indicate thespecificity of the test compound for the prenylation enzyme.

[0021] In another embodiment, a method of inhibiting the growth of acancer cell comprises contacting the cancer cell with a prenylationenzyme inhibitor according to Formula I or Formula II, where the growthof the cancer cell is inhibited.

[0022] In another embodiment, a pharmaceutically acceptable formulationcomprises a compound according to Formula I or Formula II, and apharmaceutically acceptable carrier.

[0023] These and other embodiments are described below in the detaileddescription of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention may hamper or prevent the proliferation ofcancer cells, possibly resulting in a decrease in tumor size and/ordisappearance of the cancer, to the benefit of cancer patients. It mayact by interference with cancer cell biochemistry, in which the enzymefarnesyl protein transferase, geranylgeranyl protein transferase, and/orsome other prenylation enzyme acts on the oncogenic Ras protein, RhoBprotein, or some other growth-related cellular protein. Alteration ofthe ratio of farnesylated RhoB to geranylgeranylated RhoB, for instance,through the action of farnesyl protein transferase inhibitors, isthought to have a profound effect on cancer cell proliferation. Thepresent invention may alter the farnesylation:geranylgeranylation ratiothrough the selective regulation of prenylation enzyme activity bycovalent modification of the active site of prenylation enzymes ratherthan reversible inhibition of these enzymes, as is the current practicewith farnesyl protein transferase reversible inhibitors.

[0025] The present invention is based on the effectiveness ofprenylation enzyme inhibitors for ultimately reducing and/or terminatingcancer cell proliferation through covalent or essentially irreversiblemodification of the enzyme. The potential advantages of the presentinvention over reversible inhibitors of prenyltransferase are: (1)buildup of unused substrate (e.g. FPP, Ras and RhoB proteins) cannotreverse the covalent bonding of this invention in the way reversibleinhibitors can be displaced by unused substrates, making the presentinvention more effective; and (2) the effectiveness of periodic dosingwith compounds of the present invention, in contrast to the need for theconstant presence of reversible inhibitors, may (i) adjust the activitylevel of the enzyme, decreasing toxic side effects in the patient; and(ii) minimize the ability of the cancer cell to become resistant to thetherapy.

[0026] The present invention can reduce or eliminate the unrestrainedproliferation of cancer cells through the inhibition of enzymesaffecting biochemical reactions in these cells. The specificity of theinhibitor for the target prenylation enzyme can be optimized through twoparameters: (1) structural features, including structural similarity tothe normal substrates (e.g. FPP and/or Ras), that direct or otherwisefavor the binding of the inhibitor to the active site of enzyme, and (2)a reactivity that is appropriate for the chemical groups of theprenylation enzyme, particularly those that participate in the actualprocess catalyzed by the prenylation enzyme (e.g. those chemical groupsthat directly participate in the transfer of the farnesyl group of FPPto Ras). The structurally similar feature can be a hydrophobic componenthaving a high affinity for the active site of the enzyme. For example,the active site of FTase is hydrophobic, which favors binding to itsnatural substrate FPP, also containing a hydrophobic region (i.e. thefarnesyl group). Therefore, hydrophobic inhibitors that also contain analpha-oxo epoxide or a carbon atom bearing at least one nucleofugalatom, where the carbon atom is bonded to a carbonyl (C═O) group orthiocarbonyl (C═S) group, or masked form of an alpha-oxo epoxide,carbonyl, or thiocarbonyl group, such as a group that will convert to acarbonyl or thiocarbonyl group at physiological conditions, are in manycases sufficiently reactive with the prenylation enzyme to inhibit itsactivity.

[0027] The term “alkyl,” as used alone or in combination herein, refersto an unsubstituted or optionally substituted, straight, or branchedchain saturated hydrocarbon group containing from one to twenty-fivecarbon atoms, preferably from one to fifteen carbons, such as methyl,ethyl, n-propyl, n-butyl, pentyl, hexyl, heptyl, octyl, the variousbranch chain isomers thereof, such as isopropyl, isobutyl, sec-butyl,tert-butyl, isohexyl and the like. The alkyl group may be optionallysubstituted by one or more substituents, and generally no more thanthree, and most often just one substituent. Preferred optionalsubstituents include halo, alkoxy, amino, mono- and di-substitutedamino, aryl, carboxylic acid, heterocyclo, heteroaryl, cycloalkyl,hydroxy, trifluoromethoxy and the like.

[0028] The term “lower alkyl,” as used alone or in combination herein,refers to such alkyl groups containing from one to five carbon atoms.

[0029] The term “alkoxy,” as used alone or in combination herein, refersto an alkyl group, as defined above, covalently bonded to the parentmolecule through an —O— linkage, such as methoxy, ethoxy, propoxy,isopropoxy, butoxy, t-butoxy and the like.

[0030] The term “alkoxyalkyl,” as used alone or in combination herein,refers specifically to an alkyl group substituted with an alkoxy group.

[0031] The term “aryloxy,” as used alone or in combination herein,refers to an aryl group, as defined below, covalently bonded to theparent molecule through an —O— linkage. An example of an aryloxy isphenoxy.

[0032] The term “cycloalkoxy,” as used alone or in combination herein,refers to a cycloalkyl group, as defined below, covalently bonded to theparent molecule through an —O— linkage.

[0033] The term “alkylthio,” as used alone or in combination herein,refers to an alkyl group, as defined above, covalently bonded to theparent molecule through an —S— linkage.

[0034] The term “alkenyl,” as used alone or in combination herein,refers to an alkyl group, as defined above, containing one or morecarbon-carbon double bonds, preferably two or three double bonds.Examples of alkenyl include ethenyl, propenyl, 1,3-butadienyl, and1,3,5-hexatrienyl.

[0035] The term “alkynyl,” as used alone or in combination herein,refers to an alkyl group, as defined above, containing one or morecarbon-carbon triple bonds, preferably one or two such triple bonds.

[0036] The term “cycloalkyl,” as used alone or in combination herein,refers to an unsubstituted or optionally substituted, saturated cyclichydrocarbon group containing three to eight carbon atoms. The cycloalkylgroup may optionally be substituted by one or more substituents, andgenerally no more than three, and most often just one substituent.Preferred optional substituents include alkyl, halo, amino, mono- anddi-substituted amino, aryl, hydroxy and the like.

[0037] The term “haloalkyl,” as used alone or in combination herein, isa species of alkyl as defined herein, and particularly refers to analkyl, preferably a lower alkyl, substituted with one or more halogenatoms, and preferably is a C₁ to C₄ alkyl substituted with one to threehalogen atoms. One example of a haloalkyl is trifluoromethyl. Preferredexamples of haloalkyl groups include trichloromethyl, triflouromethyl,and perflouroethyl.

[0038] The term “alkanoyl,” as used alone or in combination herein,refers to an acyl radical derived from an alkanecarboxylic acid(alkyl-C(O)—), particularly a lower alkanecarboxylic acid, and includessuch examples as acetyl, propionyl, butyryl, valeryl, and4-methylvaleryl.

[0039] The term “aroyl,” as used alone or in combination herein, meansan acyl radical derived from an aromatic carboxylic acid, such asoptionally substituted benzoic or naphthoic acids and specificallyincluding benzoyl and 1-naphthoyl.

[0040] The term “aminocarbonyl,” as used alone or in combination hereinmeans an amino-substituted carbonyl (carbamoyl or carboxamide) whereinthe amino group is a primary amino (—NH₂). Substituted aminocarbonylrefers to secondary (mono-substituted amino) or tertiary amino(disubstituted amino) group, as defined below, preferably having as asubstituent(s) a lower alkyl group.

[0041] The term “aminoalkanoyl,” as used alone or in combination herein,means an amino-substituted alkanoyl wherein the amino group is a primaryamino group (-alkyl-C(O)—NH₂). The term “substituted aminoalkanoyl”refers to related secondary (mono-substituted amino) or tertiary amino(di-substituted amino) group, as defined below.

[0042] The term “carbocycloalkyl,” as used alone or in combinationherein, refers to an unsubstituted or optionally substituted, stable,saturated or partially unsaturated monocyclic, bridged monocyclic,bicyclic, or spiro ring carbocycle of 3 to 15 carbon atoms such ascyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl,bicyclohexyl, bicyclooctyl, bicyclononyl, spirononyl and spirodecyl.Cycloalkyls are thus one specific subset of carbocycloalkyls. The term“optionally substituted” as it refers to “carbocycloalkyl” hereinindicates that the carbocycloalkyl group may be substituted at one ormore substitutable ring positions by one or more groups independentlyselected from alkyl (preferably lower alkyl), alkoxy (preferably loweralkoxy), nitro, monoalkylamino (preferably a lower alkylamino),dialkylamino (preferably a di[lower]alkylamino), cyano, halo, haloalkyl(preferably trifluoromethyl), alkanoyl, aminocarbonyl,monoalkylaminocarbonyl, dialkylaminocarbonyl, alkylamido, (preferably alower alkylamido), alkoxyalkyl (preferably a lower alkoxy[lower]alkyl),alkoxycarbonyl (preferably a lower alkoxycarbonyl), alkylcarbonyloxy(preferably a lower alkylcarbonyloxy) and aryl (preferably phenyl), saidaryl being optionally substituted by halo, lower alkyl and/or loweralkoxy groups. Generally, there is no more than one optionalsubstituent.

[0043] The term “heterocyclo,” as used alone or in combination herein,refers to an unsubstituted or optionally substituted, stable, saturated,or partially unsaturated, monocyclic, bridged monocyclic, bicyclic, orspiro ring system containing carbon atoms and other atoms selected fromnitrogen, sulfur and/or oxygen. Preferably, a heterocyclo group is a 5or 6-membered monocyclic ring or an 8-11 membered bicyclic ring thatconsists of carbon atoms and contains one, two, or three heteroatomsselected from nitrogen, oxygen and/or sulfur. Heterocyclo includesbent-fused monocyclic cycloalkyl groups having at least one suchheteroatom. The term “optionally substituted,” as it refers to“heterocyclo” herein, indicates that the heterocyclo group may besubstituted at one or more substitutable ring positions by one or moregroups independently selected from alkyl (preferably lower alkyl andincluding haloalkyl (preferably trifluoromethyl)), alkoxy (preferablylower alkoxy), nitro, monoalkylamino (preferably a lower alkylamino),dialkylamino (preferably a di[lower]alkylamino), cyano, halo, alkanoyl,aminocarbonyl, monoalkylaminocarbonyl, dialkylaminocarbonyl, alkylamido(preferably lower alkylamido), alkoxyalkyl (preferably a loweralkoxy[lower]alkyl), alkoxycarbonyl (preferably a lower alkoxycarbonyl),alkylcarbonyloxy (preferably a lower alkylcarbonyloxy) and aryl(preferably phenyl), said aryl being optionally substituted by halo,lower alkyl and lower alkoxy groups. Generally, there is no more thanone optional substituent. The heterocyclo group may be, and generallyis, attached to the parent structure through a carbon atom, oralternatively may be attached through any heteroatom of the heterocyclogroup that results in a stable structure.

[0044] The term “heteroaryl,” as used alone or in combination herein,refers to an unsubstituted or optionally substituted, stable, aromaticmonocyclic or bicyclic ring system containing carbon atoms and otheratoms selected from nitrogen, sulfur and/or oxygen. Preferably, aheteroaryl group is a 5- or 6-membered monocyclic ring (optionallybenzofused) or an 8-11 membered bicyclic ring that consists of carbonatoms and contains one, two, or three heteroatoms selected fromnitrogen, oxygen and/or sulfur. The term “optionally substituted” as itrefers to “heteroaryl” herein indicates that the heteroaryl group may besubstituted at one or more substitutable ring positions by one or moregroups independently selected from alkyl (preferably lower alkyl andincluding haloalkyl (preferably trifluoromethyl)), alkoxy (preferablylower alkoxy), nitro, monoalkylamino (preferably a lower alkylamino),dialkylamino, (preferably a di[lower]alkylamino), cyano, halo, alkanoyl,aminocarbonyl, monoalkylaminocarbonyl, dialkylaminocarbonyl, alkylamido(preferably lower alkylamido), alkoxyalkyl (preferably a loweralkoxy[lower]alkyl), alkoxycarbonyl (preferably a lower alkoxycarbonyl),alkylcarbonyloxy (preferably a lower alkylcarbonyloxy), and aryl(preferably phenyl), said aryl being optionally substituted by halo,lower alkyl, and lower alkoxy groups. Generally, there is no more thanone optional substituent. The heteroaryl group may be, and generally isattached to the parent structure through a carbon atom or alternativelymay be attached through any heteroatom of the heteroaryl group thatresults in a stable structure. In the foregoing structures it is alsocontemplated that a nitrogen could be replaced with an N-oxide. Bothheterocyclo and heteroaryl also are intended to embrace benzo fusedstructures such as 1,2-methylenedioxybenzene and 1,4-benzodioxan.Preferred examples of heteroaryl groups include pyridyl (e.g. 2-, 3-, or4-pyridyl).

[0045] The terms “halo” and “halogen,” as used alone or in combinationherein, represent fluorine, chlorine, bromine or iodine, preferablyfluorine or chlorine for enzyme affinity, and preferably chlorine,bromine, or iodine when a nucleofuge.

[0046] The term “aryl,” as used alone or in combination herein, refersto an unsubstituted or optionally substituted monocyclic or bicyclicaromatic hydrocarbon ring system having 6 to 12 ring carbon atoms.Preferred are optionally substituted phenyl, 1-naphthyl, or 2-naphthylgroups. The aryl group may optionally be substituted at one or moresubstitutable ring positions (generally at no more than three positionsand most often at one or two positions) by one or more groupsindependently selected from alkyl (including haloalkyl (preferablytrifluoromethyl and difluoromethyl)), alkenyl, alkynyl, alkoxy, aryloxy,nitro, hydroxy, amino, mono- and di-substituted amino, cyano, halo,alkanoyl, aminocarbonyl, carboxylic acid, carboxylic acid esters,carboxylic acid amide, an optionally substituted phenyl (optionallysubstituted by halo, lower alkyl and lower alkoxy groups), heterocyclo,or heteroaryl. Preferably, the aryl group is phenyl optionallysubstituted with up to four and more usually with one or two groups,preferably selected from lower alkyl, lower alkoxy, as well as cyano,trifluoromethyl, and halo.

[0047] The terms “aralkyl” and “(aryl)alkyl,” as used alone or incombination herein, are species of alkyl as defined herein, andparticularly refer to an alkyl group as defined above in which onehydrogen atom is replaced by an aryl group as defined above, and includebenzyl, and 2-phenylethyl.

[0048] The terms “(heterocyclo)alkyl” and “(heteroaryl)alkyl,” as usedalone or in combination can be considered a species of alkyl as definedherein, and particularly refer to an to an alkyl group as defined abovein which one hydrogen atom is replaced by a heterocyclo group as definedabove, or by a heteroaryl group as defined above.

[0049] The terms “alkoxycarbonyl,” as used alone or in combinationherein, mean a radical of the formula —C(O)-alkoxy, in which alkoxy isas defined above.

[0050] The term “alkylcarbonyloxy,” as used alone or in combinationherein, means a radical of the formula —O—C(O)-alkyl, in which alkyl isas defined above.

[0051] The term “alkoxyalkanoyl,” as used alone or in combinationherein, means a radical of the formula -alkyl-C(O)—O-alkyl.

[0052] The term “carboxyalkyl,” as used alone or in combination herein,means a radical of the formula -alkyl-C(O)—OH.

[0053] The term “substituted amino,” as used alone or in combinationherein, embraces both mono and di-substituted amino. These terms, alone,or in combination, mean a radical of the formula —NR′R″, where, in thecase of mono-substitution, one of R′ and R″ is a hydrogen and the otheris selected from alkyl, cycloalkyl, aryl, heterocyclo, (aryl)alkyl,(heterocyclo)alkyl, heteroaryl and hetero(aryl)alkyl; in the case ofdi-substitution, R′ and R″ are independently selected from alkyl,cycloalkyl, aryl, heterocyclo, and heteroaryl, or R′ and R″ togetherwith the nitrogen atom to which they are both attached form a three toeight-membered heterocyclo or heteroaryl radical.

[0054] The term “amido,” as used alone or in combination herein, refersto the group (—NH—) and the term “substituted amido” embraces a radicalof the formula (—NR′—) where R′ has the meaning above in connection withsubstituted amino.

[0055] The terms “alkanoylamido,” “aroylamido,”“heterocyclocarbonylamido” and “heteroaroylamido,” as used alone or incombination herein, mean groups of the formula R—C(O)—NH— where R is analkyl, aryl, heteroaryl or heterocyclo group. The terms “heteroaroyl”and “heterocyclocarbonyl,” when used alone or in combination, meangroups of the formula R—C(O)— where R is a heteroaryl or heterocyclogroup.

[0056] Unless otherwise defined, the term “optionally substituted” asused herein, refers to the substitution of a ring system at one or morepositions with one or more groups selected from: C₁-C₅ alkyl, C₁-C₅alkoxy, an optionally substituted phenyl, cyano, halo, trifluoromethyl,C₁-C₅ alkoxycarbonyl, C₁-C₅ alkyl carbonyloxy, mono- and bis-(C₁-C₅alkyl)-carboxamide, C₁-C₅ alkylamido, nitro, and mono- andbis-(C₁-C₅ alkyl) amino.

[0057] The terms “hydrophobic group” and “hydrophobic component” as usedherein, refer to any of the groups hydrogen, alkyl, alkoxy, alkoxyalkyl,aryloxy, cycloalkoxy, alkylthio, alkenyl, alkynyl, cycloalkyl,haloalkyl, alkanoyl, aroyl, aminocarbonyl, aminoalkanoyl or optionallysubstituted aminoalkanoyl, carbocycloalkyl or optionally substitutedcarbocycloalkyl, heterocyclo or optionally substituted heterocyclo,heteroaryl or optionally substituted heteroaryl, halo, aryl, aralkyl,(heterocyclo)alkyl, (heteroaryl)alkyl, alkoxycarbonyl, alkylcarbonyloxy,alkoxyalkanoyl, carboxyalkyl, amino or substituted amino, amido orsubstituted amido, and alkanoylamido as defined above having at leastsome affinity for a hydrocarbon.

[0058] The terms “nucleofugal atom” and “nucleofugal group” as usedherein refer to reactive leaving groups that, after reaction, can departwith a lone pair of electrons. Nucleofugal atoms or groups includehalogen atoms (e.g. F, Cl, Br, and I) organosulfonyloxy groups (e.g.p-toluenesulfonyloxy, p-bromobenzenesulfonyloxy, methanesulfonyloxy,trifluoromethanesulfonyloxy, etc.), acyloxy groups (e.g. CH₃CO₂—,CCl₃CO₂—), aryloxy groups (e.g. phenyl-O—), imidazolyl groups, —O—N═O,—NO₂, —OSO₃ ⁻, and —OPO₂(OH)⁻—.

[0059] It is recognized that there may be some overlap in some of thedefinitions of the various groups. Specific groups are mentioned,however, and may be particularly identified in the claims, in order toemphasize their positive inclusion in the described subject matter, asnot only an optional substituent. As used herein, when a particulargroup, generally understood to have a single point of attachment to acore structure, such as an alkyl group, is identified in connection witha structure that must have two points of attachment in the structuralcore, it is understood that the named group (e.g., alkyl) refers to theparent group with a hydrogen or a site of unsaturation removed to createthe second point of attachment so as to provide the required structure.

[0060] Compounds according to one embodiment of the present inventionhave the following generalized structural Formula I:

[0061] or a pharmaceutically acceptable salt, prodrug, or ester thereof

[0062] where A₁, A₂, and A₃, are independently selected from the groupconsisting of hydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy,cycloalkoxy, alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl,alkanoyl, aroyl, aminocarbonyl, aminoalkanoyl or optionally substitutedaminoalkanoyl, carbocycloalkyl or optionally substitutedcarbocycloalkyl, heterocyclo or optionally substituted heterocyclo,heteroaryl or optionally substituted heteroaryl, aryl, aralkyl,(heterocyclo)alkyl, (heteroaryl)alkyl, alkoxycarbonyl, alkylcarbonyloxy,alkoxyalkanoyl, and carboxyalkyl, and A₄ is selected from the groupconsisting of hydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy,cycloalkoxy, alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl,alkanoyl, aroyl, aminocarbonyl, aminoalkanoyl or optionally substitutedaminoalkanoyl, carbocycloalkyl or optionally substitutedcarbocycloalkyl, heterocyclo or optionally substituted heterocyclo,heteroaryl or optionally substituted heteroaryl, aryl, aralkyl,(heterocyclo)alkyl, (heteroaryl)alkyl, alkoxycarbonyl, alkoxyalkanoyl,carboxyalkyl, amino or substituted amino, amido or substituted amido,and A₁, A₂, A₃, and A₄ are not all hydrogen, since this would result ina compound lacking any specificity to the enzyme compared to the desiredcondition where at least one of these pendant groups has at least somespecificity.

[0063] Preferably, at least one of A₁, A₂, A₃, and A₄ is a hydrophobiccomponent designed to impart specificity of the substance for binding toand/or inactivation of FTase or GGTase. In this respect, in a preferredembodiment, A₁, A₂, A₃, and A₄ are independently selected from the groupconsisting of hydrogen, alkyl, alkenyl, alkynyl, aryl, aralkyl. Forexample, at least one of A₁, A₂, A₃, and A₄ is a branched alkenyl, whichmight be specifically a farnesyl or geranylgeranyl group. In this case,the prenylation enzyme inhibitor has a pendant group that matches thatof the substrates for which FTase and GGTase, respectively, haveaffinity. In another preferred embodiment, the group A₄ is selected fromthe group consisting of hydrogen, alkyl (e.g. methyl), haloalkyl (e.g.trichloromethyl, triflouromethyl, perflouroethyl), aryl (e.g. phenyl),and heteroaryl (e.g. 4-pyridyl). These particular groups for A₄ resultin an inhibitor having improved ability to react with the active site ofa prenylation enzyme. More specifically, and without being bound to anyparticular theory, the presence of halogen atoms in the group A₄enhances the reactivity of the inhibitor with epsilon amino groups foundin the prenylation enzyme active sites, and particularly the lysineepsilon amino group found in the active site of FTase. Additionally, thepresence of phenyl and pyridyl groups enhance the stability of a Schiffbase or imine that is believed to result from reaction of the inhibitorwith the enzyme. From the above explanation, a particularly preferredvariant of the prenylation enzyme inhibitor of the present inventionaccording to Formula I is one in which at least one of A₁, A₂, and A₃ isa hydrophobic group (e.g. a farnesyl or a geranylgeranyl group) and A₄is selected from the group consisting of alkyl, haloalkyl, aryl, andheteroaryl.

[0064] Possible methods of synthesizing prenylation inhibitor compoundsof the present invention are provided below for compounds according toFormula I and Formula II as described above. In the case of alpha-oxoepoxides within the scope of Formula I, the treatment of thealpha,beta-unsaturated carbonyl compound with alkaline hydrogenperoxide, is depicted below:

[0065] Another synthesis possibility for compounds of Formula I is theSharpless epoxidation of the allylic alcohol, followed by oxidation ofthe alcohol. This method results in the stereospecific formation ofchiral alpha-oxo epoxides, and is depicted below:

[0066] Another class of compounds contemplated within the scope of theinvention has the following generalized structural Formula II:

A—Y—(C═Z)—CX₁X₂X₃  (Formula II)

[0067] or a pharmaceutically acceptable salt, prodrug, or ester thereof

[0068] where Y is a heteroatom or heteroatomic group selected from thegroup consisting of O, NH, NA′, and S; where,

[0069] when Y is O, A and A′ are independently selected from the groupconsisting of hydrogen, alkyl, alkoxyalkyl, alkylthio, alkenyl, alkynyl,cycloalkyl, haloalkyl, carbocycloalkyl or optionally substitutedcarbocycloalkyl, heterocyclo or optionally substituted heterocyclo,heteroaryl or optionally substituted heteroaryl, aryl, aralkyl,(heterocyclo)alkyl, (heteroaryl)alkyl, carboxyalkyl, amino orsubstituted amino, amido or substituted amido, and alkanoylamido;

[0070] when Y is S, A and A′ are independently selected from the groupconsisting of hydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy,cycloalkoxy, alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl,carbocycloalkyl or optionally substituted carbocycloalkyl, heterocycloor optionally substituted heterocyclo, heteroaryl or optionallysubstituted heteroaryl, aryl, aralkyl, (heterocyclo)alkyl,(heteroaryl)alkyl, carboxyalkyl, amino or substituted amino, amido orsubstituted amido, and alkanoylamido; and,

[0071] when Y is NH or NA′, A and A′ are independently selected from thegroup consisting of hydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy,cycloalkoxy, alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl,alkanoyl, aroyl, aminocarbonyl, aminoalkanoyl or optionally substitutedaminoalkanoyl, carbocycloalkyl or optionally substitutedcarbocycloalkyl, heterocyclo or optionally substituted heterocyclo,heteroaryl or optionally substituted heteroaryl, halo, aryl, aralkyl,(heterocyclo)alkyl, (heteroaryl)alkyl, alkoxycarbonyl, alkylcarbonyloxy,alkoxyalkanoyl, carboxyalkyl, amino or substituted amino, amido orsubstituted amido, and alkanoylamido;

[0072] Z is O or S, resulting in a carbonyl or thiocarbonyl group; and,

[0073] X₁, X₂, and X₃ are independently selected from the groupconsisting of hydrogen, halogen, organosulfonyloxy,bromobenzenesulfonyloxy, methanesulfonyloxy,trifluoromethanesulfonyloxy, acyloxy, aryloxy, imidazolyl, —O—N═O, —NO₂,—OSO₃ ⁻ and —OPO₂(OH)—. The groups X₁, X₂ and X₃ are not all hydrogen,as this particular case would result in the compound having an attachedmethyl group which is relatively unreactive compared to the desiredcondition where at least one of these pendant groups is a nucleofugalgroup. In a preferred embodiment, A, and optionally A′, areindependently selected from the group consisting of hydrogen, alkyl,alkenyl, alkynyl, aryl, aralkyl. In another preferred embodiment, atleast one of A, and optionally A′ is a branched alkenyl, which may bespecifically a farnesyl or geranylgeranyl group.

[0074] According to the possibilities for Formula II, there exists acarbonyl variation, where Z is oxygen, and also a thiocarbonylvariation, where Z is sulfur. Preferred enzyme inhibitor compoundswithin the generalized structural Formula II can be characterized asalpha-haloesters or alpha-halothioesters where Y is an oxygen atom, X₁and X₂ are hydrogen, and X₃ is a halogen. In the case of the carbonylvariation of Formula II, a preferred class of prenylation inhibitors isobtained when X₁ is oxygen, such that the inhibitor will now have twocarbonyl functions, and X₂ is methyl. These preferred compounds may alsobe categorized as pyruvic acid derivatives.

[0075] As mentioned, the portion of the compound represented by any of Aaids in the selective, noncovalent binding or affinity of the inventivecompounds for prenyltransferases. Also, the carbonyl or thiocarbonylgroup of compounds represented by Formula II, combined with an adjacentnucleofuge-bearing carbon atom, can subsequently bond to theprenyltransferase active site, thereby regulating the level of activityof the prenyltransferase by hampering access of substrates to the activesite residues and/or other mechanisms such as by inducing conformationalchanges in the prenyltransferase that affect its catalytic ability. Theregulation of catalytic activity of the prenyltransferase can also beachieved by total inactivation of a portion of the prenyltransferasemolecules while leaving some molecules completely unmodified.

[0076] It is possible to prepare compounds within the scope of FormulaII according to the pathway provided below, where, for example, A is afarnesyl subsitutent, Y and Z are oxygen, X₁ and X₂ are hydrogen, and X₃is bromine:

[0077] The pathway outlined below depicts the synthesis of anothercompound of Formula II, having a hydrophobic substituent comprising aphenyl group and a polyether functionality:

[0078] Other embodiments of the invention include a pharmaceuticallyacceptable salt, prodrug, or ester of the compounds of Formula I orFormula II. By way of example, for compounds having structural FormulaII, the carbonyl groups can be masked in various forms including ahydrate [C(OH)₂], a hemiacetal or hemiketal [C(OH)(OR′)], an acetal or aketal [C(OR′)(OR″)], an acylal or related compound[C(OC(═O)R)OC(═O)R″)], a bisulfite addition compound [C(OH)(SO₃ ⁻)], anenol (C═COH), an enol ether (C═COR′), an enol ester [C═COC═(═O)R′], andso forth, wherein R′ and R″ are independently selected from the groupconsisting of hydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy,cycloalkoxy, alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl,alkanoyl, aroyl, aminocarbonyl, aminoalkanoyl or optionally substitutedaminoalkanoyl, carbocycloalkyl or optionally substitutedcarbocycloalkyl, heterocyclo or optionally substituted heterocyclo,heteroaryl or optionally substituted heteroaryl, halo, aryl, aralkyl,(heterocyclo)alkyl, (heteroaryl)alkyl, alkoxycarbonyl, alkylcarbonyloxy,alkoxyalkanoyl, carboxyalkyl, amino or substituted amino, amido orsubstituted amido, and alkanoylamido. Likewise, prenylation enzymeinhibitors according to the thiocarbonyl variation of Formula II mayalso include masked thiocarbonyl groups, in which the oxygen atoms inthe masked groups according to the above description are replaced bysulfur atoms. Of course, it is possible that, where the masked groupsaccording to the above description contain more than one oxygen atom, acombination of oxygen and sulfur atoms may actually be included in themasked group. Such masked carbonyl or thiocarbonyl groups may producethe carbonyl or thiocarbonyl groups of the prenylation enzyme inhibitorsof the present invention under physiological conditions.

[0079] Some cancer cells in which farnesylation of Ras is blockedalternatively employ the related prenylation reactiongeranylgeranylation to attach a hydrophobic group to Ras, accomplishingmembrane localization and continued cancerous behavior of the cell. Theenzyme that attaches the geranylgeranyl group to Ras protein tofacilitate localization at the inner surface of the cancer cell membraneis geranylgeranyl protein transferase, also known as proteingeranylgeranyltransferase (referred to here as GGTase). Thegeranylgeranyl group becomes attached to Ras by reaction withgeranylgeranyl diphosphate, also known as geranylgeranyl pyrophosphate(referred to here as GGPP). Stated otherwise, GGTase catalyzes thefollowing reaction, in which Ras becomes attached to geranylgeranylgroup by displacement of pyrophosphate (P₂O₇ ⁴⁻, referred to here asPP_(i)):

GGTase .

Ras+GGP→geranylgeranyl-Ras+PP_(i)

[0080] The newly formed geranylgeranyl-Ras localizes at the innersurface of the cancer cell membrane and causes the cancer cell to dividewithout restraint. Thus, a key target in a strategy to retard cancercell proliferation is the enzyme GGTase. By reducing or destroyingGGTase activity, either in combination with regulation of Rasfarnesylation or independently, Ras geranylgeranylation may be alsoregulated, which in turn should further hinder the ability of the cancercell to divide and proliferate through localization of Ras at its innermembrane surface. As noted previously, regulation of RhoBgeranlygeranylation by use of inhibitors of the present invention isalso contemplated as a means for retarding and/or terminating cancercell growth.

[0081] To more precisely align the structure of the inhibitors of thepresent invention with the active sites of FTase, GGTase, or otherenzymes, variation of the distance between the covalent-bonding groupand the farnesyl-mimicking or geranylgeranyl-mimicking group is achievedthrough altering the length of a “spacer” between such groups. Forexample, inhibitors representative of the carbonyl variation ofstructural Formula II may be more precisely tailored to inhibit eitherFTase or GGTase activity by altering the spacer length as representedbelow:

[0082] where the value of n, representing the number of carbon atomsbetween the respective farnesyl and geranylgeranyl groups, willgenerally range from 0 to about 10, although instances where longerchains are required for alignment with other types of enzymes arereadily recognizable to the ordinary skilled artisan having regard forthis disclosure.

[0083] Inhibitors of the present invention may also incorporate anaromatic group for enhanced binding to the hydrophobic binding site ofFTase or GGTase. Such compounds are exemplified by the followingspecific enzyme inhibitors according to the carbonyl variation ofstructural Formula II, although numerous other possible embodiments ofthis type of compound are of course possible and readily apparent to oneof ordinary skill in the art, having regard for this disclosure:

[0084] Three additional possibilities are represented below, where thelast two have an A group that is selective for the FTase active siteover the GGTase and squalene synthase active sites, thus conferringadded specificity for the desired target enzyme.

[0085] The inhibitors of the present invention are applicable inparticular to the reduction in prenylation activity of the enzymesfarnesyl protein transferase and geranylgeranyl protein transferase.Without wishing to be bound by any particular theory or reactionmechanism, a hypothetical pathway illustrating FTase inhibition usingthe alpha-oxo epoxide prenylation enzyme inhibitors, according toFormula I of the present invention, is shown below:

[0086] As shown, the FTase active site contains two amino acid residuesthat are involved in the reaction with the inhibitor, namely His-248 andLys-294. The rest of the enzyme is conveniently represented as E. Thesetwo residues are in close proximity as a consequence of their normalrole in binding the natural substrate FPP at its terminal phosphate. Asshown above, nucleophilic attack by the His imidazole group results inepoxide ring opening, thus making the epoxide oxygen formally anucleofuge. In addition to alkylation of the imidazole ring, the nearbyepsilon-amino group of the Lys forms a Schiff base or imine with thealdehyde group of the alpha-oxo epoxide. The result of the abovereactions is the crosslinking of two active site residues. The resultingcrosslinked structure irreversibly precludes the FTase active siteresidues from catalyzing prenylation reactions, thus impairing theenzyme's overall functioning.

[0087] Analogous reaction mechanisms can be postulated for inhibitorcompounds of the present invention according to both the carbonyl andthiocarbonyl variations of Formula II. In these cases, the nucleofugalatom or group adjacent to a carbonyl group can react with theaforementioned active site residues to crosslink them in an analogousmanner to the mechanism shown above, with an accompanying release of thenucleofugal group.

[0088] Preferably, the inhibitor is administered under proper conditionsand in a concentration such that its presence in the prenylation systemreduces prenylation activity by at least about 50%, more preferably atleast about 75%, and even more preferably by at least about 90%.Pharmaceutical formulations can be prepared by combining appropriateamounts of the inhibitor in a pharmaceutically acceptable carrier,diluent, or excipient. In such formulations, the inhibitor is typicallypresent in an amount from about 0.1-20% by weight, and more commonlyfrom about 1-10%.

[0089] Combinations of this invention with other anticancer agents toproduce synergistic effects of benefit to the patient are also possible.This might be based on two strategies. One is to interfere withdifferent biochemical processes to increase tumor cell killing. Anotheris to hamper development of drug resistance, which is less likely tooccur simultaneously in tumor cells exposed to anticancer agents basedon interference with different biochemical pathways in the tumor cells.

[0090] In summary an improved method of interference with proteinprenylation in tumor cells has been described that may prevent or hamperthe proliferation of tumor cells, possibly resulting in a decrease intumor size and/or disappearance of the cancer, to the benefit of cancerpatients.

EXAMPLES 1-2

[0091] Two alpho-oxo epoxides according to Formula I of the presentinvention were synthesized according to procedures set forth in H. Yaoand D. E. Richardson, J. Am. Chem. Soc. 2000, 122, 3220-3221 and also inC. A. Bunton and G. J. Minkoff, J. Chem. Soc. 1949, 665-670. Thecompounds were then tested for their inhibition of the growth of variouscancer cells. These compounds had, as their A₂ substituent, farnesyl andgeranylgeranyl groups, respectively. These inhibitors had structuralformulas as shown below.

[0092] The compounds were tested for growth inhibition in a variety ofhuman cancer cell lines, according to procedures described by K. J.Okolotowicz, W. L. Lee, R. F. Hartman, S. R. Lefler, and S. D. Rose,Inactivation of Protein Farnesyltransferase by Active-Site-TargetedDicarbonyl Compounds, Arch. Pharm. Pharm. Med. Chem. 2001, 334, 194-202.Results of biological testing of these compounds are summarized in Table1, where the GI₅₀ value represents the concentration of inhibitorcompound required to effect a 50% reduction in cell growth (i.e. 50%inhibition). TABLE 1 Inhibition of Cancer Cell Growth by Alpha-oxoEpoxides GI₅₀/molar GI₅₀/molar Human cancer cell line Compound RG-22Compound RG-23 Breast (MCF-7) 14 × 10⁻⁶ 8.9 × 10⁻⁶  Prostate (DU-145) 27× 10⁻⁶ 28 × 10⁻⁶ Central nervous syst. (SF268) 30 × 10⁻⁶ 42 × 10⁻⁶Pancreatic (BXPC-3) 67 × 10⁻⁶ 51 × 10⁻⁶ Colon (KM20L2) 95 × 10⁻⁶ 61 ×10⁻⁶ Lung (NCI-H460) 117 × 10⁻⁶  63 × 10⁻⁶

[0093] Results show that both compounds are extremely active forinhibiting cell growth in various human cancer cell lines in culture. Infact, one of the GI₅₀ values was below 10 micromoles/liter.Additionally, the compounds were active against mouse P388 leukemiacells in culture. In these cases, compound RG-22 exhibited an ED₅₀ of26×10⁻⁶ M, and RG-23 exhibited an ED₅₀ of only 11×10⁻⁶ M. Based on theseresults, the anticancer activity of these compounds is confirmed.

EXAMPLES 3-4

[0094] Two alpha-halo carbonyl compounds were also synthesized asdecribed previously herein and tested for their inhibition of the growthof various cancer cells. These compounds had substituent farnesyl groupsas well as substituent nucleofugal halogen atoms. The inhibitors hadstructural formulas as shown below:

[0095] The compounds were tested for growth inhibition in a variety ofhuman cancer cell lines, as described in Examples 1-2. Results of the invitro cell culture testing of these compounds are summarized in Table 2,which provides the associated GI₅₀ values. TABLE 2 Cell Culture Resultswith Alpha-halo Carbonyl Compounds Example 3 Example 4 Human cancer cellline GI₅₀/molar GI₅₀/molar Colon (HT-29) 10⁻⁴ to 10⁻⁵ 10⁻⁴ to 10⁻⁵Colorectal (Colo-205) 10⁻⁴ to 10⁻⁵ 10⁻⁴ to 10⁻⁵ NSC Lung (H-460) 1.1 ×10⁻⁵ 1.4 × 10⁻⁵ Prostate (PC-3) 7.9 × 10⁻⁶ 1.6 × 10⁻⁵ Acute myeloidleukemia (HL-60) Above 10⁻⁴  10⁻⁹ to 10⁻¹⁰ Fibrosarcoma (HT-1080) 10⁻⁵to 10⁻⁶ 10⁻⁴ to 10⁻⁵ Urinary bladder (T-24) 10⁻⁴ to 10⁻⁵ 10⁻⁴ to 10⁻⁵Colon (Caco-2) Above 10⁻⁴ 10⁻⁴ to 10⁻⁵

[0096] Again, results show that the compounds provide effectiveinhibition of cancer cell growth, even at low concentrations.

What is claimed is:
 1. A method for inhibiting a prenylation enzyme, themethod comprising contacting the prenylation enzyme with a compound ofFormula I:

or a pharmaceutically acceptable salt, prodrug, or ester thereof whereA₁, A₂, and A₃, are independently selected from the group consisting ofhydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy, cycloalkoxy, alkylthio,alkenyl, alkynyl, cycloalkyl, haloalkyl, alkanoyl, aroyl, aminocarbonyl,aminoalkanoyl or optionally substituted aminoalkanoyl, carbocycloalkylor optionally substituted carbocycloalkyl, heterocyclo or optionallysubstituted heterocyclo, heteroaryl or optionally substitutedheteroaryl, aryl, aralkyl, (heterocyclo)alkyl, (heteroaryl)alkyl,alkoxycarbonyl, alkylcarbonyloxy, alkoxyalkanoyl, and carboxyalkyl, andA₄ is selected from the group consisting of hydrogen, alkyl, alkoxy,alkoxyalkyl, aryloxy, cycloalkoxy, alkylthio, alkenyl, alkynyl,cycloalkyl, haloalkyl, alkanoyl, aroyl, aminocarbonyl, aminoalkanoyl oroptionally substituted aminoalkanoyl, carbocycloalkyl or optionallysubstituted carbocycloalkyl, heterocyclo or optionally substitutedheterocyclo, heteroaryl or optionally substituted heteroaryl, aryl,aralkyl, (heterocyclo)alkyl, (heteroaryl)alkyl, alkoxycarbonyl,alkoxyalkanoyl, carboxyalkyl, amino or substituted amino, amido orsubstituted amido, and alkanoylamido, with the proviso that A₁, A₂, A₃,and A₄ are not all hydrogen.
 2. The method of claim 1 where theprenylation enzyme is farnesyl protein transferase or geranylgeranylprotein transferase.
 3. The method of claim 1 where the activity of theprenylation enzyme is reduced by at least about 50%.
 4. The method ofclaim 1 where the activity of the prenylation enzyme is reduced by atleast about 75%.
 5. The method of claim 1 where the activity of theprenylation enzyme is reduced by at least about 90%.
 6. The method ofclaim 1 where A₄ is selected from the group consisting of hydrogen,alkyl, haloalkyl, aryl, and heteroaryl.
 7. The method of claim 6 whereA₄ is selected from the group consisting of methyl, trichloromethyl,triflouromethyl, perflouroethyl, phenyl, 2-pyridyl, 3-pyridyl, and4-pyridyl.
 8. The method of claim 1 where A₁, A₂, A₃, and A₄ areindependently selected from the group consisting of hydrogen, alkyl,alkenyl, alkynyl, aryl, aralkyl.
 9. The method of claim 8 where at leastone of A₁, A₂, A₃, and A₄ is a branched alkenyl group.
 10. The method ofclaim 9 where at least one of A₁, A₂, A₃, and A₄ is farnesyl orgeranylgeranyl.
 11. A method for inhibiting a prenylation enzyme, themethod comprising contacting the prenylation enzyme a compound ofFormula IIA: A—Y—(C═O)—CX₁X₂X₃  (Formula IIA) or a pharmaceuticallyacceptable salt, prodrug, or ester thereof where: Y is a heteroatom orheteroatomic group independently selected from the group consisting ofO, NH, NA′, and S; where, when Y is O, A and A′ are independentlyselected from the group consisting of hydrogen, alkyl, alkoxyalkyl,alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl, carbocycloalkyl oroptionally substituted carbocycloalkyl, heterocyclo or optionallysubstituted heterocyclo, heteroaryl or optionally substitutedheteroaryl, aryl, aralkyl, (heterocyclo)alkyl, (heteroaryl)alkyl,carboxyalkyl, amino or substituted amino, amido or substituted amido,and alkanoylamido; when Y is S, A and A′ are independently selected fromthe group consisting of hydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy,cycloalkoxy, alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl,carbocycloalkyl or optionally substituted carbocycloalkyl, heterocycloor optionally substituted heterocyclo, heteroaryl or optionallysubstituted heteroaryl, aryl, aralkyl, (heterocyclo)alkyl,(heteroaryl)alkyl, carboxyalkyl, amino or substituted amino, amido orsubstituted amido, and alkanoylamido; and, when Y is NH or NA′, A and A′are independently selected from the group consisting of hydrogen, alkyl,alkoxy, alkoxyalkyl, aryloxy, cycloalkoxy, alkylthio, alkenyl, alkynyl,cycloalkyl, haloalkyl, alkanoyl, aroyl, aminocarbonyl, aminoalkanoyl oroptionally substituted aminoalkanoyl, carbocycloalkyl or optionallysubstituted carbocycloalkyl, heterocyclo or optionally substitutedheterocyclo, heteroaryl or optionally substituted heteroaryl, halo,aryl, aralkyl, (heterocyclo)alkyl, (heteroaryl)alkyl, alkoxycarbonyl,alkylcarbonyloxy, alkoxyalkanoyl, carboxyalkyl, amino or substitutedamino, amido or substituted amido, and alkanoylamido; and, X₁, X₂, andX₃ are independently selected from the group consisting of hydrogen,halogen, organosulfonyloxy, bromobenzenesulfonyloxy, methanesulfonyloxy,trifluoromethanesulfonyloxy, acyloxy, aryloxy, imidazolyl, —O—N═O, —NO₂,—OSO₃ ⁻, and —OPO₂(OH)⁻, with the proviso that X₁, X₂, and X₃ are notall hydrogen.
 12. The method of claim 11 where the prenylation enzyme isfarnesyl protein transferase or geranylgeranyl protein transferase. 13.The method of claim 11 where the activity of the prenylation enzyme isreduced by at least about 50%.
 14. The method of claim 11 where theactivity of the prenylation enzyme is reduced by at least about 75%. 15.The method of claim 11 where the activity of the prenylation enzyme isreduced by at least about 90%.
 16. The method of claim 11 where Y isoxygen; X₁ and X₂ are hydrogen; and X₃ is a halogen.
 17. The method ofclaim 11 where X, is O and X₂ is methyl.
 18. The method of claim 11where A and A′ are independently selected from the group consisting ofhydrogen, alkyl, alkenyl, alkynyl, aryl, aralkyl.
 19. The method ofclaim 18 where at least one of A and A′ is a branched alkenyl group 20.The method of claim 19 where at least one of A and A′ is farnesyl orgeranylgeranyl.
 21. A method for inhibiting a prenylation enzyme, themethod comprising contacting the prenylation enzyme with a compound ofFormula IIB: A—Y—(C═S)—CX₁X₂X₃  (Formula IIB) or a pharmaceuticallyacceptable salt, prodrug, or ester thereof where: Y is a heteroatom orheteroatomic group independently selected from the group consisting ofO, NH, NA′, and S; where, when Y is O, A and A′ are independentlyselected from the group consisting of hydrogen, alkyl, alkoxyalkyl,alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl, carbocycloalkyl oroptionally substituted carbocycloalkyl, heterocyclo or optionallysubstituted heterocyclo, heteroaryl or optionally substitutedheteroaryl, aryl, aralkyl, (heterocyclo)alkyl, (heteroaryl)alkyl,carboxyalkyl, amino or substituted amino, amido or substituted amido,and alkanoylamido; when Y is S, A and A′ are independently selected fromthe group consisting of hydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy,cycloalkoxy, alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl,carbocycloalkyl or optionally substituted carbocycloalkyl, heterocycloor optionally substituted heterocyclo, heteroaryl or optionallysubstituted heteroaryl, aryl, aralkyl, (heterocyclo)alkyl,(heteroaryl)alkyl, carboxyalkyl, amino or substituted amino, amido orsubstituted amido, and alkanoylamido; and, when Y is NH or NA′, A and A′are independently selected from the group consisting of hydrogen, alkyl,alkoxy, alkoxyalkyl, aryloxy, cycloalkoxy, alkylthio, alkenyl, alkynyl,cycloalkyl, haloalkyl, alkanoyl, aroyl, aminocarbonyl, aminoalkanoyl oroptionally substituted aminoalkanoyl, carbocycloalkyl or optionallysubstituted carbocycloalkyl, heterocyclo or optionally substitutedheterocyclo, heteroaryl or optionally substituted heteroaryl, halo,aryl, aralkyl, (heterocyclo)alkyl, (heteroaryl)alkyl, alkoxycarbonyl,alkylcarbonyloxy, alkoxyalkanoyl, carboxyalkyl, amino or substitutedamino, amido or substituted amido, and alkanoylamido; and X₁, X₂, and X₃are independently selected from the group consisting of hydrogen,halogen, organosulfonyloxy, bromobenzenesulfonyloxy, methanesulfonyloxy,trifluoromethanesulfonyloxy, acyloxy, aryloxy, imidazolyl, —O—N═O, —NO₂,—OSO₃ ⁻, and —OPO₂(OH)⁻, with the proviso that X₁, X₂, and X₃ are notall hydrogen.
 22. The method of claim 21 where the prenylation enzyme isfarnesyl protein transferase or geranylgeranyl protein transferase. 23.The method of claim 21 where the activity of the prenylation enzyme isreduced by at least about 50%.
 24. The method of claim 21 where theactivity of the prenylation enzyme is reduced by at least about 75%. 25.The method of claim 21 where the activity of the prenylation enzyme isreduced by at least about 90%.
 26. The method of claim 21 where Y isoxygen; X₁ and X₂ are hydrogen; and X₃ is a halogen.
 27. The method ofclaim 21 where A and A′ are independently selected from the groupconsisting of hydrogen, alkyl, alkenyl, alkynyl, aryl, aralkyl.
 28. Themethod of claim 27 where at least one of A and A′ is a branched alkenylgroup.
 29. The method of claim 28 where at least one of A and A′ isfarnesyl or geranylgeranyl.
 30. A method of screening compounds aspotential anti-tumor agents, the method comprising contacting aprenylation enzyme with a test compound of Formula I:

or a pharmaceutically acceptable salt, prodrug, or ester thereof whereA₁, A₂, and A₃, are independently selected from the group consisting ofhydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy, cycloalkoxy, alkylthio,alkenyl, alkynyl, cycloalkyl, haloalkyl, alkanoyl, aroyl, aminocarbonyl,aminoalkanoyl or optionally substituted aminoalkanoyl, carbocycloalkylor optionally substituted carbocycloalkyl, heterocyclo or optionallysubstituted heterocyclo, heteroaryl or optionally substitutedheteroaryl, aryl, aralkyl, (heterocyclo)alkyl, (heteroaryl)alkyl,alkoxycarbonyl, alkylcarbonyloxy, alkoxyalkanoyl, and carboxyalkyl, andA₄ is selected from the group consisting of hydrogen, alkyl, alkoxy,alkoxyalkyl, aryloxy, cycloalkoxy, alkylthio, alkenyl, alkynyl,cycloalkyl, haloalkyl, alkanoyl, aroyl, aminocarbonyl, aminoalkanoyl oroptionally substituted aminoalkanoyl, carbocycloalkyl or optionallysubstituted carbocycloalkyl, heterocyclo or optionally substitutedheterocyclo, heteroaryl or optionally substituted heteroaryl, aryl,aralkyl, (heterocyclo)alkyl, (heteroaryl)alkyl, alkoxycarbonyl,alkoxyalkanoyl, carboxyalkyl, amino or substituted amino, amido orsubstituted amido, and alkanoylamido, with the proviso that A₁, A₂, A₃,and A₄ are not all hydrogen, and measuring prenylation activity of theenzyme, where a reduction in prenylation activity renders the testcompound a candidate anti-tumor agent.
 31. The method of claim 30 wherethe reduction in prenylation activity is at least about 50% to renderthe test compound a candidate anti-tumor agent.
 32. The method of claim30 where a reduction in prenylation activity is at least about 75% torender the test compound a candidate anti-tumor agent.
 33. The method ofclaim 30 where a reduction in prenylation activity is at least about 90%to render the test compound a candidate anti-tumor agent.
 34. The methodof claim 30 where the prenylation enzyme is farnesyl protein transferasegeranylgeranyl protein transferase.
 35. The method of claim 30 where,prior to the contacting step, a natural substrate of the prenylationenzyme is added to the test compound to compete therewith and indicatethe specificity of the test compound for the prenylation enzyme.
 36. Themethod of claim 35 where the natural substrate of the prenylation enzymeis farnesyl pyrophosphate or geranylgeranyl pyrophosphate.
 37. A methodof screening compounds as potential anti-tumor agents, the methodcomprising contacting a prenylation enzyme with a test compound ofFormula IIA: A—Y—(C═O)—CX₁X₂X₃  (Formula IIA) or a pharmaceuticallyacceptable salt, prodrug, or ester thereof where: Y is a heteroatom orheteroatomic group independently selected from the group consisting ofO, NH, NA′, and S; where, when Y is O, A and A′ are independentlyselected from the group consisting of hydrogen, alkyl, alkoxyalkyl,alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl, carbocycloalkyl oroptionally substituted carbocycloalkyl, heterocyclo or optionallysubstituted heterocyclo, heteroaryl or optionally substitutedheteroaryl, aryl, aralkyl, (heterocyclo)alkyl, (heteroaryl)alkyl,carboxyalkyl, amino or substituted amino, amido or substituted amido,and alkanoylamido; when Y is S, A and A′ are independently selected fromthe group consisting of hydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy,cycloalkoxy, alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl,carbocycloalkyl or optionally substituted carbocycloalkyl, heterocycloor optionally substituted heterocyclo, heteroaryl or optionallysubstituted heteroaryl, aryl, aralkyl, (heterocyclo)alkyl,(heteroaryl)alkyl, carboxyalkyl, amino or substituted amino, amido orsubstituted amido, and alkanoylamido; and, when Y is NH or NA′, A and A′are independently selected from the group consisting of hydrogen, alkyl,alkoxy, alkoxyalkyl, aryloxy, cycloalkoxy, alkylthio, alkenyl, alkynyl,cycloalkyl, haloalkyl, alkanoyl, aroyl, aminocarbonyl, aminoalkanoyl oroptionally substituted aminoalkanoyl, carbocycloalkyl or optionallysubstituted carbocycloalkyl, heterocyclo or optionally substitutedheterocyclo, heteroaryl or optionally substituted heteroaryl, halo,aryl, aralkyl, (heterocyclo)alkyl, (heteroaryl)alkyl, alkoxycarbonyl,alkylcarbonyloxy, alkoxyalkanoyl, carboxyalkyl, amino or substitutedamino, amido or substituted amido, and alkanoylamido, and X₁, X₂, and X₃are independently selected from the group consisting of hydrogen,halogen, organosulfonyloxy, bromobenzenesulfonyloxy, methanesulfonyloxy,trifluoromethanesulfonyloxy, acyloxy, aryloxy, imidazolyl, —O—N═O, —NO₂,—OSO₃ ⁻, and —OPO₂(OH)⁻, with the proviso that X₁, X₂, and X₃ are notall hydrogen, and measuring prenylation activity of the enzyme, where areduction in prenylation activity renders the test compound a candidateanti-tumor agent.
 38. The method of claim 37 where the reduction inprenylation activity is at least about 50% to render the test compound acandidate anti-tumor agent.
 39. The method of claim 37 where a reductionin prenylation activity is at least about 75% to render the testcompound a candidate anti-tumor agent.
 40. The method of claim 37 wherea reduction in prenylation activity is at least about 90% to render thetest compound a candidate anti-tumor agent.
 41. The method of claim 37where the prenylation enzyme is farnesyl protein transferasegeranylgeranyl protein transferase.
 42. The method of claim 37 where,prior to the contacting step, a natural substrate of the prenylationenzyme is added to the test compound to compete therewith and indicatethe specificity of the test compound for the prenylation enzyme.
 43. Themethod of claim 42 where the natural substrate of the prenylation enzymeis farnesyl pyrophosphate or geranylgeranyl pyrophosphate.
 44. A methodof screening compounds as potential anti-tumor agents, the methodcomprising contacting a prenylation enzyme with a test compound ofFormula IIB: A—Y—(C═S)—CX₁X₂X₃  (Formula IIB) or a pharmaceuticallyacceptable salt, prodrug, or ester thereof where: Y is a heteroatom orheteroatomic group selected from the group consisting of O, NH, NA′, andS; where, when Y is O, A and A′ are independently selected from thegroup consisting of hydrogen, alkyl, alkoxyalkyl, alkylthio, alkenyl,alkynyl, cycloalkyl, haloalkyl, carbocycloalkyl or optionallysubstituted carbocycloalkyl, heterocyclo or optionally substitutedheterocyclo, heteroaryl or optionally substituted heteroaryl, aryl,aralkyl, (heterocyclo)alkyl, (heteroaryl)alkyl, carboxyalkyl, amino orsubstituted amino, amido or substituted amido, and alkanoylamido; when Yis S, A and A′ are independently selected from the group consisting ofhydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy, cycloalkoxy, alkylthio,alkenyl, alkynyl, cycloalkyl, haloalkyl, carbocycloalkyl or optionallysubstituted carbocycloalkyl, heterocyclo or optionally substitutedheterocyclo, heteroaryl or optionally substituted heteroaryl, aryl,aralkyl, (heterocyclo)alkyl, (heteroaryl)alkyl, carboxyalkyl, amino orsubstituted amino, amido or substituted amido, and alkanoylamido; and,when Y is NH or NA′, A and A′ are independently selected from the groupconsisting of hydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy,cycloalkoxy, alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl,alkanoyl, aroyl, aminocarbonyl, aminoalkanoyl or optionally substitutedaminoalkanoyl, carbocycloalkyl or optionally substitutedcarbocycloalkyl, heterocyclo or optionally substituted heterocyclo,heteroaryl or optionally substituted heteroaryl, halo, aryl, aralkyl,(heterocyclo)alkyl, (heteroaryl)alkyl, alkoxycarbonyl, alkylcarbonyloxy,alkoxyalkanoyl, carboxyalkyl, amino or substituted amino, amido orsubstituted amido, and alkanoylamido, and X₁, X₂, and X₃ areindependently selected from the group consisting of hydrogen, halogen,organosulfonyloxy, bromobenzenesulfonyloxy, methanesulfonyloxy,trifluoromethanesulfonyloxy, acyloxy, aryloxy, imidazolyl, —O—N═O, —NO₂,—OSO₃ ⁻, and —OPO₂(OH)⁻, with the proviso that X₁, X₂, and X₃ are notall hydrogen, and measuring prenylation activity of the enzyme, where areduction in prenylation activity renders the test compound a candidateanti-tumor agent.or having the structural formula.
 45. The method ofclaim 44 where the reduction in prenylation activity is at least about50% to render the test compound a candidate anti-tumor agent.
 46. Themethod of claim 44 where a reduction in prenylation activity is at leastabout 75% to render the test compound a candidate anti-tumor agent. 47.The method of claim 44 where a reduction in prenylation activity is atleast about 90% to render the test compound a candidate anti-tumoragent.
 48. The method of claim 44 where the prenylation enzyme isfarnesyl protein transferase geranylgeranyl protein transferase.
 49. Themethod of claim 44 where, prior to the contacting step, a naturalsubstrate of the prenylation enzyme is added to the test compound tocompete therewith and indicate the specificity of the test compound forthe prenylation enzyme.
 50. The method of claim 49 where the naturalsubstrate of the prenylation enzyme is farnesyl pyrophosphate orgeranylgeranyl pyrophosphate.
 51. A method of inhibiting the growth of acancer cell, the method comprising contacting the cancer cell with acompound of Formula I:

or a pharmaceutically acceptable salt, prodrug, or ester thereof whereA₁, A₂, and A₃, are independently selected from the group consisting ofhydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy, cycloalkoxy, alkylthio,alkenyl, alkynyl, cycloalkyl, haloalkyl, alkanoyl, aroyl, aminocarbonyl,aminoalkanoyl or optionally substituted aminoalkanoyl, carbocycloalkylor optionally substituted carbocycloalkyl, heterocyclo or optionallysubstituted heterocyclo, heteroaryl or optionally substitutedheteroaryl, aryl, aralkyl, (heterocyclo)alkyl, (heteroaryl)alkyl,alkoxycarbonyl, alkylcarbonyloxy, alkoxyalkanoyl, and carboxyalkyl, andA₄ is selected from the group consisting of hydrogen, alkyl, alkoxy,alkoxyalkyl, aryloxy, cycloalkoxy, alkylthio, alkenyl, alkynyl,cycloalkyl, haloalkyl, alkanoyl, aroyl, aminocarbonyl, aminoalkanoyl oroptionally substituted aminoalkanoyl, carbocycloalkyl or optionallysubstituted carbocycloalkyl, heterocyclo or optionally substitutedheterocyclo, heteroaryl or optionally substituted heteroaryl, aryl,aralkyl, (heterocyclo)alkyl, (heteroaryl)alkyl, alkoxycarbonyl,alkoxyalkanoyl, carboxyalkyl, amino or substituted amino, amido orsubstituted amido, and alkanoylamido, with the proviso that A₁, A₂, A₃,and A₄ are not all hydrogen.
 52. The method of claim 52 where the cancercell is selected from the group consisting of colon, colorectal, NSClung, prostate, acute myeloid leukemia, fibrosarcoma, and urinarybladder cancer cells.
 53. The method of claim 52 where the GI₅₀concentration is less than about 10⁻⁴ molar.
 54. A method of inhibitingthe growth of a cancer cell, the method comprising contacting the cancercell with a compound of Formula IIA: A—Y—(C═O)—CX₁X₂X₃  (Formula IIA) ora pharmaceutically acceptable salt, prodrug, or ester thereof where: Yis a heteroatom or heteroatomic group independently selected from thegroup consisting of O, NH, NA′, and S; where, when Y is O, A and A′ areindependently selected from the group consisting of hydrogen, alkyl,alkoxyalkyl, alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl,carbocycloalkyl or optionally substituted carbocycloalkyl, heterocycloor optionally substituted heterocyclo, heteroaryl or optionallysubstituted heteroaryl, aryl, aralkyl, (heterocyclo)alkyl,(heteroaryl)alkyl, carboxyalkyl, amino or substituted amino, amido orsubstituted amido, and alkanoylamido; when Y is S, A and A′ areindependently selected from the group consisting of hydrogen, alkyl,alkoxy, alkoxyalkyl, aryloxy, cycloalkoxy, alkylthio, alkenyl, alkynyl,cycloalkyl, haloalkyl, carbocycloalkyl or optionally substitutedcarbocycloalkyl, heterocyclo or optionally substituted heterocyclo,heteroaryl or optionally substituted heteroaryl, aryl, aralkyl,(heterocyclo)alkyl, (heteroaryl)alkyl, carboxyalkyl, amino orsubstituted amino, amido or substituted amido, and alkanoylamido; and,when Y is NH or NA′, A and A′ are independently selected from the groupconsisting of hydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy,cycloalkoxy, alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl,alkanoyl, aroyl, aminocarbonyl, aminoalkanoyl or optionally substitutedaminoalkanoyl, carbocycloalkyl or optionally substitutedcarbocycloalkyl, heterocyclo or optionally substituted heterocyclo,heteroaryl or optionally substituted heteroaryl, halo, aryl, aralkyl,(heterocyclo)alkyl, (heteroaryl)alkyl, alkoxycarbonyl, alkylcarbonyloxy,alkoxyalkanoyl, carboxyalkyl, amino or substituted amino, amido orsubstituted amido, and alkanoylamido, and X₁, X₂, and X₃ areindependently selected from the group consisting of hydrogen, halogen,organosulfonyloxy, bromobenzenesulfonyloxy, methanesulfonyloxy,trifluoromethanesulfonyloxy, acyloxy, aryloxy, imidazolyl, —O—N═O, —NO₂,—OSO₃ ⁻, and —OPO₂(OH)⁻, with the proviso that X₁, X₂, and X₃ are notall hydrogen.
 55. The method of claim 54 where the cancer cell isselected from the group consisting of colon, colorectal, NSC lung,prostate, acute myeloid leukemia, fibrosarcoma, and urinary bladdercancer cells.
 56. The method of claim 54 where the GI₅₀ concentration isless than about 10⁻⁴ molar.
 57. A method of inhibiting the growth of acancer cell, the method comprising contacting the cancer cell with acompound of Formula IIB: A—Y—(C═S)—CX₁X₂X₃  (Formula IIB) or apharmaceutically acceptable salt, prodrug, or ester thereof where: Y isa heteroatom or heteroatomic group independently selected from the groupconsisting of O, NH, NA′, and S; where, when Y is O, A and A′ areindependently selected from the group consisting of hydrogen, alkyl,alkoxyalkyl, alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl,carbocycloalkyl or optionally substituted carbocycloalkyl, heterocycloor optionally substituted heterocyclo, heteroaryl or optionallysubstituted heteroaryl, aryl, aralkyl, (heterocyclo)alkyl,(heteroaryl)alkyl, carboxyalkyl, amino or substituted amino, amido orsubstituted amido, and alkanoylamido; when Y is S, A and A′ areindependently selected from the group consisting of hydrogen, alkyl,alkoxy, alkoxyalkyl, aryloxy, cycloalkoxy, alkylthio, alkenyl, alkynyl,cycloalkyl, haloalkyl, carbocycloalkyl or optionally substitutedcarbocycloalkyl, heterocyclo or optionally substituted heterocyclo,heteroaryl or optionally substituted heteroaryl, aryl, aralkyl,(heterocyclo)alkyl, (heteroaryl)alkyl, carboxyalkyl, amino orsubstituted amino, amido or substituted amido, and alkanoylamido; and,when Y is NH or NA′, A and A′ are independently selected from the groupconsisting of hydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy,cycloalkoxy, alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl,alkanoyl, aroyl, aminocarbonyl, aminoalkanoyl or optionally substitutedaminoalkanoyl, carbocycloalkyl or optionally substitutedcarbocycloalkyl, heterocyclo or optionally substituted heterocyclo,heteroaryl or optionally substituted heteroaryl, halo, aryl, aralkyl,(heterocyclo)alkyl, (heteroaryl)alkyl, alkoxycarbonyl, alkylcarbonyloxy,alkoxyalkanoyl, carboxyalkyl, amino or substituted amino, amido orsubstituted amido, and alkanoylamido, and X₁, X₂, and X₃ areindependently selected from the group consisting of hydrogen, halogen,organosulfonyloxy, bromobenzenesulfonyloxy, methanesulfonyloxy,trifluoromethanesulfonyloxy, acyloxy, aryloxy, imidazolyl, —O—N═O, —NO₂,—OSO₃ ⁻, and —OPO₂(OH)⁻, with the proviso that X₁, X₂, and X₃ are notall hydrogen.
 58. The method of claim 57 where the cancer cell isselected from the group consisting of colon, colorectal, NSC lung,prostate, acute myeloid leukemia, fibrosarcoma, and urinary bladdercancer cells.
 59. The method of claim 57 where the GI₅₀ concentration isless than about 10⁻⁴ molar.
 60. A pharmaceutical formulation comprisinga compound of Formula I:

or a pharmaceutically acceptable salt, prodrug, or ester thereof whereA₁, A₂, and A₃ are independently selected from the group consisting ofhydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy, cycloalkoxy, alkylthio,alkenyl, alkynyl, cycloalkyl, haloalkyl, alkanoyl, aroyl, aminocarbonyl,aminoalkanoyl or optionally substituted aminoalkanoyl, carbocycloalkylor optionally substituted carbocycloalkyl, heterocyclo or optionallysubstituted heterocyclo, heteroaryl or optionally substitutedheteroaryl, aryl, aralkyl, (heterocyclo)alkyl, (heteroaryl)alkyl,alkoxycarbonyl, alkylcarbonyloxy, alkoxyalkanoyl, and carboxyalkyl, andA₄ is selected from the group consisting of hydrogen, alkyl, alkoxy,alkoxyalkyl, aryloxy, cycloalkoxy, alkylthio, alkenyl, alkynyl,cycloalkyl, haloalkyl, alkanoyl, aroyl, aminocarbonyl, aminoalkanoyl oroptionally substituted aminoalkanoyl, carbocycloalkyl or optionallysubstituted carbocycloalkyl, heterocyclo or optionally substitutedheterocyclo, heteroaryl or optionally substituted heteroaryl, aryl,aralkyl, (heterocyclo)alkyl, (heteroaryl)alkyl, alkoxycarbonyl,alkoxyalkanoyl, carboxyalkyl, amino or substituted amino, amido orsubstituted amido, and alkanoylamido, with the proviso that A₁, A₂, A₃,and A₄ are not all hydrogen, and a pharmaceutically acceptable carrier,diluent, or excipient.
 61. A pharmaceutical formulation comprising acompound of Formula IIA: A—Y—(C═O)—CX₁X₂X₃  (Formula IIA) or apharmaceutically acceptable salt, prodrug, or ester thereof where: Y isa heteroatom or heteroatomic group independently selected from the groupconsisting of O, NH, NA′, and S; where, when Y is O, A and A′ areindependently selected from the group consisting of hydrogen, alkyl,alkoxyalkyl, alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl,carbocycloalkyl or optionally substituted carbocycloalkyl, heterocycloor optionally substituted heterocyclo, heteroaryl or optionallysubstituted heteroaryl, aryl, aralkyl, (heterocyclo)alkyl,(heteroaryl)alkyl, carboxyalkyl, amino or substituted amino, amido orsubstituted amido, and alkanoylamido; when Y is S, A and A′ areindependently selected from the group consisting of hydrogen, alkyl,alkoxy, alkoxyalkyl, aryloxy, cycloalkoxy, alkylthio, alkenyl, alkynyl,cycloalkyl, haloalkyl, carbocycloalkyl or optionally substitutedcarbocycloalkyl, heterocyclo or optionally substituted heterocyclo,heteroaryl or optionally substituted heteroaryl, aryl, aralkyl,(heterocyclo)alkyl, (heteroaryl)alkyl, carboxyalkyl, amino orsubstituted amino, amido or substituted amido, and alkanoylamido; and,when Y is NH or NA′, A and A′ are independently selected from the groupconsisting of hydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy,cycloalkoxy, alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl,alkanoyl, aroyl, aminocarbonyl, aminoalkanoyl or optionally substitutedaminoalkanoyl, carbocycloalkyl or optionally substitutedcarbocycloalkyl, heterocyclo or optionally substituted heterocyclo,heteroaryl or optionally substituted heteroaryl, halo, aryl, aralkyl,(heterocyclo)alkyl, (heteroaryl)alkyl, alkoxycarbonyl, alkylcarbonyloxy,alkoxyalkanoyl, carboxyalkyl, amino or substituted amino, amido orsubstituted amido, and alkanoylamido, and X₁, X₂, and X₃ areindependently selected from the group consisting of hydrogen, halogen,organosulfonyloxy, bromobenzenesulfonyloxy, methanesulfonyloxy,trifluoromethanesulfonyloxy, acyloxy, aryloxy, imidazolyl, —O—N═O, —NO₂,—OSO₃ ⁻, and —OPO₂(OH)⁻, with the proviso that X₁, X₂, and X₃ are notall hydrogen, and a pharmaceutically acceptable carrier, diluent, orexcipient.
 62. A pharmaceutical formulation comprising a compound ofFormula IIB: A—Y—(C═S)—CX₁X₂X₃  (Formula IIB) or a pharmaceuticallyacceptable salt, prodrug, or ester thereof where: Y is a heteroatom orheteroatomic group independently selected from the group consisting ofO, NH, NA′, and S; where when Y is O, A and A′ are independentlyselected from the group consisting of hydrogen, alkyl, alkoxyalkyl,alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl, carbocycloalkyl oroptionally substituted carbocycloalkyl, heterocyclo or optionallysubstituted heterocyclo, heteroaryl or optionally substitutedheteroaryl, aryl, aralkyl, (heterocyclo)alkyl, (heteroaryl)alkyl,carboxyalkyl, amino or substituted amino, amido or substituted amido,and alkanoylamido; when Y is S, A and A′ are independently selected fromthe group consisting of hydrogen, alkyl, alkoxy, alkoxyalkyl, aryloxy,cycloalkoxy, alkylthio, alkenyl, alkynyl, cycloalkyl, haloalkyl,carbocycloalkyl or optionally substituted carbocycloalkyl, heterocycloor optionally substituted heterocyclo, heteroaryl or optionallysubstituted heteroaryl, aryl, aralkyl, (heterocyclo)alkyl,(heteroaryl)alkyl, carboxyalkyl, amino or substituted amino, amido orsubstituted amido, and alkanoylamido; and, when Y is NH or NA′, A and A′are independently selected from the group consisting of hydrogen, alkyl,alkoxy, alkoxyalkyl, aryloxy, cycloalkoxy, alkylthio, alkenyl, alkynyl,cycloalkyl, haloalkyl, alkanoyl, aroyl, aminocarbonyl, aminoalkanoyl oroptionally substituted aminoalkanoyl, carbocycloalkyl or optionallysubstituted carbocycloalkyl, heterocyclo or optionally substitutedheterocyclo, heteroaryl or optionally substituted heteroaryl, halo,aryl, aralkyl, (heterocyclo)alkyl, (heteroaryl)alkyl, alkoxycarbonyl,alkylcarbonyloxy, alkoxyalkanoyl, carboxyalkyl, amino or substitutedamino, amido or substituted amido, and alkanoylamido, and X₁, X₂, and X₃are independently selected from the group consisting of hydrogen,halogen, organosulfonyloxy, bromobenzenesulfonyloxy, methanesulfonyloxy,trifluoromethanesulfonyloxy, acyloxy, aryloxy, imidazolyl, —O—N═O, —NO₂,—OSO₃ ⁻, and —OPO₂(OH)⁻, with the proviso that X₁, X₂, and X₃ are notall hydrogen, and a pharmaceutically acceptable carrier, diluent, orexcipient.
 63. A compound having a formula selected from the groupconsisting of:

or a pharmaceutically acceptable salt, prodrug, or ester thereof.
 64. Apharmaceutical composition comprising a compound of claim 63 and apharmaceutically acceptable carrier, diluent, or excipient.
 65. A methodof inhibiting a prenylation enzyme comprising contacting the enzyme witha compound of claim
 63. 66. A method of treating cancer comprisingadministering an effective amount of a pharmaceutical composition ofclaim
 60. 67. A method of treating cancer comprising administering aneffective amount of a pharmaceutical composition of claim
 61. 68. Amethod of treating cancer comprising administering an effective amountof a pharmaceutical composition of claim 62.